Adored by the Network: Cartoon Network decided the pilot should become its own series, and the show has spanned four entire seasons without a single threat of having it yanked off the air, despite its scary nature. This show is also one of the few cancelled originals to still air on a regular basis. The series was rerun on Cartoon Network for 13 years, up to 2015, always finding a way back on the schedule, it is even featured on Cartoon Network's website and even its app.
After the show completed its four-season, 52-episode run (typical for most cartoon series on cable networks such as Cartoon Network and Nickelodeon), many fans petitioned for a continuation, which both the network and John R. Dilworth considered, but ultimately, Dilworth decided not to continue with any further episodes or seasons. On the same token, a (possibly theatrical) movie was confirmed to be in the works, however, it never came to fruition.
Approval of God: John Dilworth doesn't deny a single one of the Wild Mass Guesses made about the show, as he wants to leave it just as open to interpretation as any other work of art.
Fan Nickname: The "Perfect Trumpet Thingy" or "Eustace's Trumpet" for the blue thing in the first of Courage's nightmares in "Perfect" and "Violin Girl" for the Demon Head in "Courage in the Big Stinkin' City".
Courage, Muriel, and Eustace together as a group are usually called "the Bagges" or "the Bagge family" by fans.
Furry Fandom: Courage is beloved among furries. They (as well as pretty much other artist) generally draw him very endearingly.
The pilot, The Chicken From Outer Space, partly plays this straight and partly averts it. It's not on the Season 1 DVD, but John R Dilworth sells it through his online store, and it's easily found on YouTube.
Recycled Script: Season 3's "Curtain of Cruelty" has a similar plot to Season 2's "The Tower of Dr. Zalost", with anger and hostility infecting the Nowhere townspeople instead of sadness and depression.
The Other Darrin: Lionel Wilson was replaced by Arthur Anderson as the voice of Eustace in the middle of the third season after the former died; despite this, audio of Wilson was still used when Eustace said his more common lines, laughed, or screamed (the difference was very noticeable). In the 2014 special, Anderson was replaced by none other than Wallace Shawn (who didn't even try to give Eustace a Scottish accent, using his normal voice instead; by comparison, Muriel's voice actress, Thea White, was able to flawlessly recreate her original voice). For Cartoon Network's 20th anniversary promo, Eustace is voiced by Tom Kenny.
Talking to Himself: Will Ryan must have had a lot of fun arguing with himself throughout "The Duck Brothers".
Urban Legend of Zelda: When "The Duck Brothers" originally aired, Will Ryan's impersonation of Ringo Starr was so flawless, everyone thought it was actually him.
One early idea was for each cartoon to have a live-action bridging segment, with John Dilworth playing "Spaceman Dilly."
So many fans were saddened by the show's ending that an online petition was formed, and sent to both Cartoon Network and Stretch Films, asking for a continuation. Because of this, a fifth season of the series was considered, but ultimately never came to be.
On the same token, because of the series' popularity with fans, a movie was also up for consideration (whether theatrical or TV was never made clear), but nothing ever came out of it due to the poor box office performance of The Powerpuff Girls Movie..
Series composer Jody Gray wanted to release a CD soundtrack of the show's music scoring and songs, and even asked fans to submit requests of specifics they'd like to be included in the soundtrack. Once again, nothing ever materialized.
Way back when, Dilworth was pitching his indie short The Dirty Birdie to Hanna-Barbera for the What a Cartoon! program, but they deemed the short unsuitable for TV, and Dilworth pitched what was to be his next indie effort The Chicken from Outer Space in order to receive funding for it, and the rest was history.
When Cartoon Network started developing the series in 1999, the show was set to be produced and developed by Hanna-Barbera, which handled the What a Cartoon! anthology series that featured the show's pilot short. Dilworth eventually sent the production to his Stretch Films Studios, but it would've been interesting to see how Hanna-Barbera would've developed the series following its What a Cartoon! short.
The 2014 short "The Fog of Courage" was part of an idea by John R Dilworth and Cartoon Network to revive the series, but the network changed its mind to pursue bigger projects.
Word of God: One of the few oddities John Dilworth willingly explained was the hole Courage's tooth: it's a symbol that nature is imperfect, and how one can still affirm in life when they know that evil exists.